6 MAREK IWAŃSKI 1 RYSZARD ORZECHOWSKI 2 Kielce University of Technology THE EFFECT OF RUBBER AND SYNTHETIC WAX ON THE SELECTED PROPERTIES OF BITUMEN 50/70 A b s t r a c t This article presents the results and the analysis of the study of the impact of rubber and synthetic wax on the properties of bitumen 50/70 with an addition of 5 20% of granular rubber and 1 2% of synthetic wax. The tests conducted within the study measured penetration, softening point, Fraass breaking point, elastic recovery and dynamic viscosity. Based on the study, the penetration index and the plasticity temperature range were calculated. The results show that the rubber modified with synthetic wax significantly improves the properties of bitumen 50/70. Keywords: bitumen, rubber modification, synthetic wax 1. Introduction Research centres around the world are looking for ways to improve the quality and extend the durability of road pavements. One of the possible methods to enhance the pavement performance is the use of polymer modified bitumen or bitumen with other modifiers to produce asphalt mixtures. As the environmental factor is very important, many countries including Poland are conducting diverse research and development projects involving recycled rubber from tyre waste. This paper presents the results of the study of bitumen 50/70 modified with rubber and synthetic wax Fischer-Tropsch. 2. Characteristics of the material Regular bitumen 50/70 in compliance with PN- EN was used in the study. The samples were collected in accordance with the requirements of PN- EN 58 and prepared for testing in accordance with PN-EN Asphalt-rubber binder is a mixture of hot asphalt and crumb rubber gradation 0 0.8mm derived from scrap tires and synthetic wax produced by Fischer-Tropsch. The crumb rubber from car tires added to the asphalt (wet process technology) improves the binder properties [1]. Using the synthetic wax it is possible to reduce energy consumption and lower the viscosity necessary to surround the grains of the aggregate and increase the resistance to permanent deformation [2]. 3. Selection of test parameters The optimal binder properties are obtained at 200 C for 4 hours of stirring [3]. According to [4] the optimum thermal conditions for the rubber to bind with asphalt are in the temperature range of C. Time of mixing asphalt with the rubber is long and continues for 3 8 hours. The use of synthetic wax does not cause major problems, since the waxes melt at the temperature of C and are soluble in the asphalt binder simply by mixing. According to the national [6, 3, 4] and the foreign tests [7, 8] the binder annealing temperature was set at 180 C and the soaking time was set at 60 minutes. 4. Course of study To determine the effect of rubber and synthetic wax on the properties of bitumen 50/70, 15 series of test has been performed, and were marked as symbols: GXDY. G0D0 G0D1 G0D2 G5D0 G5D1 G5D2 G10D0 G10D1 G10D2 G15D0 G15D1 G15D2 G20D0 G20D1 G20D2 where: X content of rubber in the binder modified with rubber and the synthetic wax [%], Y content of synthetic wax in the binder modified with rubber and the synthetic wax [%], G15D2 means that in the binder modified with rubber and the synthetic 5

7 Marek Iwański, Ryszard Orzechowski wax, there is 15% of rubber and 2% of synthetic wax, G0D0 means that in the binder modified with rubber and the synthetic wax, there is 0% of rubber and 0% of synthetic wax basically it is a standard asphalt without any other additives. The rubber in the form of crumb was added to the asphalt in the amount of 5%, 10%, 15% and 20% relative to the total weight of the binder. Synthetic wax was added to the asphalt in the amount of 1% and 2% relative to the total weight of binder. All the ingredients were mixed at 180 C for 5 minutes with a high speed mixer. While mixing, the sample containers were placed in a special thermos, in order to reduce the heat loss. After mixing, the mixture was heated in an oven at 180 C for 60 minutes. After the heating process, the following tests has been made: penetration process at the temperature of 25 C according to PN-EN 1426; softening temperature with the method of Ring and Ball according to PN-EN1427; Fraass breaking point according to PN-EN 12593; elastic recovery in the temperature of 25 C according to PN-EN 13398; dynamic viscosity designation according to PN- EN Tests results Vertical bars indicate confidence intervals of 0.95 (Figures of 1, 2, 5 and 6). The content of wax makes asphalt harder and stiffer in the operating temperature, it also reduces the penetration and increases the softening temperature. In the similar way, the rubber addition reduces penetration and increases the softening point (Figs 1-2). Penetration index is a measure of the sensitivity of asphalt. The lower the PI, the asphalt is thermally more sensitive [9]. Penetration index was calculated on the basis of the penetration at 25 C and softening temperature of PiK according to PN-EN [10]. With the increase of rubber and the synthetic wax content in the binder, the penetration index increases as well (Fig. 3). PI results for bitumen can be shaped roughly from 3 to +3. The lower the value of PI, the bitumen softens quicker when heated rapidly, which basically means that it is more thermally sensitive [9]. The asphalt binder modified with rubber and synthetic wax characterizes with better penetration index. The plasticity temperature range TZP increases while increasing the content of rubber and synthetic wax in the binder (Fig. 4). TZP = t PiK t łam (1) where: t PiK softening point, C, t łam Fraass breaking point. Penetration [0,1 mm] Softening point [ C] Penetration Index ,0 3,5 3,0 2,5 2,0 1,5 1,0 0,5 0,0-0,5-1,0-1,5-2, Rubber Content [%] Fig. 1. Penetration value at 25 C in relation to rubber and synthetic wax content Rubber Content [%] Fig. 2. Softening point Ball and ring value in relation to rubber and synthetic wax content Rubber Content [%] Fig. 3. Penetration index PI versus rubber and synthetic wax content D0 D1 D2 D0 D1 D2 D0 D1 D2 6

8 THE EFFECT OF RUBBER AND SYNTHETIC WAX ON THE SELECTED PROPERTIES OF BITUMEN 50/70 Temperature range of plasticity TZP [ o C] Breaking point [ o C] Rubber Content [%] Fig. 4. Influence of rubber and synthetic wax on the plasticity temperature range TZP of 50/50 bitumen G0 G5 G10 G15 G20 Content Rubber [%] Fig. 5. Fraass breaking point versus rubber and synthetic wax content Synthetic wax without any crumb rubber effect rising of the breaking point, which makes the properties of the binder worse. In the same way the crumb rubber addition in the amount of up to 10% makes the binder properties much worse. Over the 10% of rubber addiction in the binder, the Fraass breaking point decreases rapidly, which points to better binder properties (Fig. 5). While increasing the rubber content in the binder, the value of the elastic recovery increases. With the rubber content of 20% the elastic recovery is about 80%. The addition of synthetic wax (rubber content from 5 to 15%) results in increasing the elastic recovery (Fig. 6). All the samples cracked before reaching 200 mm. The addition of crumb rubber significantly increases the asphalt viscosity. The addition of synthetic wax increases the viscosity of the mineral asphalt mixture at the operating temperatures, and in the production temperature effects by lowering it. However, the D0 D1 D2 D0 D1 D2 reduction of viscosity of the synthetic wax with a rubber content of 1% and 2%, is very slight. Figure 7 presents a summary results of studies of dynamic viscosity versus temperature for all the 15 series. Elastic Recovery [%] Dynamic viscosity [Pa. s] G0 G5 G10 G15 G20 Content Rubber [%] Fig. 6. Effect of rubber and synthetic wax on elastic recovery of bitumen 50/ ,0 5000,0 500,0 50,0 5,0 0, Temperature [ o C] Fig. 7. Dynamic viscosity versus temperature D0 D1 D2 Series G0D0 Series G0D1 Series G0D2 Series G5D0 Series G5D1 Series G5D2 Series G10D0 Series G10D1 Series G10D2 Series G15D0 Series G15D1 Series G15D2 Series G20D0 Series G20D1 Series G20D2 6. Conclusions Tests and analyzes allow us to draw the following conclusions: 1. Addition of rubber and synthetic wax at the temperature of 180 C improves the properties of the bitumen 50/ The 50/70 asphalt, with the addition of rubber, produced at the temperature of 180 C has a lower penetration index and a higher softening point. The addition of synthetic wax results in a further reduction of the penetration index while the softening point increase. 7

12 ELŻBIETA URBAŃSKA-GALEWSKA 1 PATRYK DENIZIAK 2 Gdańsk University of Technology THE INFLUENCE OF APPLYING SUPPLEMENTARY WEB PLATES ON STRUCTURAL JOINT MOMENT RESISTANCE AND ROTATIONAL STIFFNESS A b s t r a c t Continual trend to simplify structural elements and find less time-consuming solutions on construction site as well as inevitable increase in labour costs determine for instance elimination of those technological steps that are difficult to automation. Welding additional reinforcements and web stiffeners are great examples of such a step. The method presented in EN [8] is a result of long-term studies focused on calculating the moment resistance and stiffness of joints without transverse web stiffeners. Design calculations shown in this paper are based on resistance and stiffness growth analysis applying supplementary web plates. Authors consider validity of this solution due to construction effort and building durability remembering about minimization of the costs. Keywords: steel structures, bolted joints, supplementary web plates, T-stubs with 4 bolts 1. Introduction Constant aspiration for production costs minimization results in uninterrupted researching for simplification of construction elements in steel civil engineering sector as well. In the era of high level of steel elements producing industrialization those research projects are mainly focused on construction details simplifying due to the labour costs. It was common to eliminate those technical steps that were difficult to automation, for instance hole drilling. Cutting, adjusting and welding details for instance transverse web stiffeners or additional reinforcements were always (and still are) kind of slowing down steps in automated production systems. Resignation of those joint stiffening elements contributes to develop research into so-called semi-rigid connections whose stiffness is smaller than traditional rigid joints but still far from pinned ones. Long-term studies focused on semi-rigid links result in unusually complex and laborious design procedures that are legitimized in European Standard [8]. Mentioned rules allow not only to design structural frame joints but also determine the stiffness of the connections. Considering the rotational stiffness in calculations allows to use bending moment redistribution in frames which can result in successive savings in beam cross-sections dimensions, therefore mass of the whole structure. This paper shows exact designs examples that despite of using labour-intensive calculation procedures which allows to remove transverse web stiffeners are forcing the construction engineers to apply supplementary web plates increasing the resistance and rotational stiffness of column panel in shear, transverse compression and tension. Applying such supplementary web plates is nearly as laborious as welding transverse web stiffeners so it is contrary to the basic semi-rigid joints assumption focused mainly on production costs minimization. Furthermore, applying those supplementary web plates makes it impossible to hot dip galvanize as a corrosion protection. 2. Analysis of moment resistance and rotational stiffness in frame joint A connection of a beam and a column is usually a critical point in steel frames made of H or I sections where the beam height is decisive. Designing fullstrength joints (it means that the joint design moment resistance M j,rd is higher than the plastic moment resistance of the beam M b,pl,rd ) is possible in case of 11

13 Elżbieta Urbańska-Galewska, Patryk Deniziak local increase of the beam height near the top of the column applying oblique reinforcements so-called haunched beam. The second possibility is to increase the number of bolts in each rows from two to four. This increase is available only when the width of the H or I section beams reaches at least 300 mm. In this paper frame eaves joint moment resistances are analysed in detail. The structure is made of S235 steel. HEB 400 is a column cross-section and as a beam section HEA 300, HEA 400, HEA 500 and HEA 600 are used interchangeably. Figure 1 shows the structure of the analysed end plate connection. There are four different bolt diameters (M16, M20, M25, M30) applied for each cross section of the beam. What is more, every bolt diameter has four different end plate thicknesses (t p = 15, 20, 25 and 30 mm) taken into consideration. Bolts grade 8.8 are applied. The component method defining the joint moment resistance M j,rd and the stiffness S j,ini is described in many publications [1, 7] and also in European Standard [8] as well. This method considers resistance of every basic joint component showing the designers its influence on a general joint resistance so it is possible to identify the critical basic joint component (the weakest element in the connection). Table 1 shows calculated result combinations of the resistance in each analysed case presenting critical Fig. 1. Structure of the analysed end plate connection Table 1. Values of moment resistance and rotational stiffness for joint without supplementary web plates (beam HEA 300) Bolts class 8.8 M16 M20 M24 M30 End plate thickness [mm] Critical basic joint component 1 st bolts row 2 nd bolts row 3 rd bolts row M j,rd [knm] S j,ini [knm/rad] 15 End plate Bolts Bolts End plate Bolts Bolts Bolts Bolts Bolts Bolts Bolts Bolts End plate Bolts End plate End plate Bolts Column web Column flange Column web Bolts Column flange Column web Bolts End plate End plate Column web End plate Bolts Column web Column web Bolts Column web Column web Bolts Column web End plate End plate Column web Column web Column web Column web Column web Column web Column web Column web Column web Column web

15 Elżbieta Urbańska-Galewska, Patryk Deniziak web plates in semi-rigid joints. Before and after reinforcement results are presented in Table 3. Table 3. Increase of moment resistance and rotational stiffness for joint with one supplementary web plate (beam HEA 300) comparing with joint without supplementary web plate Bolts class 8.8 End plate Δ M j,rd Δ S j,ini thickness [mm] [%] [%] M M In the presented case the moment resistance increase is placed between 14% and 37% and the stiffness increase between 43% and 47%. 4. Summary and conclusions Taken parametric analysis explicitly confirms high effectiveness of applying supplementary web plates as a method of reinforcing the column web panel. Figure 3. shows comparing of the moment resistance increase. Fig. 3. Comparison of moment resistance for joint (column HEB 400 and beam HEA 300) before and after reinforcement using supplementary web plate Stiffness of analysed joint (column HEB 400 and beam HEA 300) including one-sided web plate reinforcement is shown in Figure 4. The comparison is made for joints with M24 and M30 bolts. It is easy to notice the influence of the column web resistance (without reinforcement) on the resistance of whole connection and strong growth of the moment resistance in joints with web plates. The end plate thickness has visible influence as well. Fig. 4. Comparison of moment resistance for joint (column HEB 400 and beam HEA 300) before and after reinforcement using supplementary web plate This effect is impossible to attain using traditional transverse web stiffeners extending beam flanges [3]. An alternative solution to the method of joints reinforcing with supplementary web plates, which is a very effective method, is applying joints with so-called haunched beams (additional material and labour) or applying bigger hot formed cross-sections. There is a very important question appearing at this stage if it is actually possible to combine aspiration to eliminate expensive and laborious technological solutions with structure designing in an effective way focused on complete steel consumption. Furthermore applying such plates makes corrosion protection hard to put on galvanized elements. Due to a huge time consuming joint designing process according to [8] it would be advisable to create tables helpful in designing semi-rigid connections including traditional reinforcement by transverse web stiffeners and one- and double-sided supplementary web plates as well. Computer applications as resistance calculators wouldn t be even as effective tool for designers as tables and diagrams that allows to do wide-ranging and deep analysis and consider different variants of the construction. References [1] Bródka J., Kozłowski A.: Sztywność i nośność węzłów podatnych (Moment resistance and stiffness of semirigid joints), Oficyna Wydawnicza Politechniki Rzeszowskiej, Rzeszów-Białystok [2] Bródka J., Kozłowski A., Ligocki I., Łaguna J., Ślęczka L.: Projektowanie i obliczanie połączeń i węzłów konstrukcji stalowych (Designing and calculation of connections and joints in steel constructions), Polskie Wydawnictwo Techniczne, Rzeszów

19 MARIAN GIŻEJOWSKI 1 ZBIGNIEW STACHURA 2 Institute of Building Engineering Faculty of Civil Engineering Warsaw University of Technology PARTIAL FACTORS FOR THE MEMBER STABILITY RESISTANCE OF STEEL STRUCTURES A b s t r a c t Up-to-date investigations carried out by the authors of this paper were concerned with the analysis of cross-section resistance utilization ratios (RURs) of statically determinate elements of steel floor construction, assuming that elements are fully restrained against overall instability. Numerical values of RURs were predicted according to Eurocodes implemented in Poland as standards PN-EN and according to Polish standards PN-B being substituted. For the cross section resistance according to Eurocodes, partial resistance factors were taken as unity, as it has been recommended in the Polish National Annex, and their differentiated, modified values according to authors own proposal. Hereafter, a discussion on the evaluation of partial factors for the member stability resistance (buckling of columns and lateral-torsional buckling of beams) is taken place. The proposal for the evaluation of partial factor values in the whole range of element slenderness is presented together with a statistical analysis of section and member resistances taking into account the authors proposal developed. Keywords: steel elements, cross-section resistance, member resistance, partial factors, statistical analysis 1. Introduction The present contribution is a continuation of authors investigations presented in Giżejowski and Stachura [1] and referred to the evaluation of cross-section resistance partial factors of statically determinate structural elements in steel floor constructions. Results included different sensitivity of cross section to local buckling, i.e. the effect of section class. This paper extends the previously undertaken topic of section resistance analysis of steel floor structural elements towards their overall stability resistance, considering the steel grades S235 and S355, the most frequently used in practice. Analysis of safety requirements according to the same computational model of the steel floor structure was carried out for main floor structural elements, and under the condition of resistance utilization ratios equalization using two different packages of design codes taken into account. Resistance utilization factors (RURs) obtained with reference to the code PN-90/B [2] and associated PN-B codes were accounted for together with the code PN-EN [3] and associated PN-EN codes. 2. Methodology and results Partial factors γ M resulting from the analysis of safety requirements as described above are as follows: in case of elements bent in the plane of greater cross section moment of inertia and subjected to lateral-torsional buckling: Mb, Rk, EN MEd, PN γm = γs = Mb, Rk, PN MEd, EN (1) M c, Rk, EN χ ( γg, PN + γq, PN ψ) LT = γ s M φ γ + γ ψ ( ) c, Rk, PN LT G, EN Q, EN in case of elements axially compressed and subjected to different modes of buckling: 18

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